A windshield heating assembly having an electric resistance heating element in the parking area of windshield wipers

Abstract: An arrangement for heating upper (32) and lower (30) windshield wiper blades parked proximate the lower edge of a windshield (10) utilizes an electric heating grid placed against the inside surface of the windshield, substantially in alignment with the parked wiper blades. The electric heating grid (42,44,46) is comprised of a first wire (42) in alignment with the lower blade (30), an intermediate wire (44) and an upper wire (46) in alignment with the upper blade (32). The wires have opposite ends which are connected to busses that are disposed at the lower edge of the windshield, the busses having leads for connection to power circuitry. The power circuitry includes a climate control system having a switch which is rotatable to a defrost position. When the switch is rotated to the defrost position so that the climate control system defrosts the windshield, current flows through the grid. As long as the switch is in the defrost position, the current continues to flow. The power circuitry also includes a windshield wiper deicing switch which operates independently of the defrost switch. Associated with the windshield wiper deicing switch is a timer which opens the closed deicing switch after a selected interval of time. This arrangement provides an inexpensive reliable system for deicing windshield wiper blades because the wires are disposed on the windshield against the inside surface of the windshield.

Description: The present invention relates to arrangements for heating windshield wipers. More particularly, the present invention relates to arrangements for heating windshield wipers utilizing electric current. In freezing weather, windshield wiper blades can become frozen to the windshield of a motor vehicle when the wiper blades are in their parked position proximate the lower edge of the windshield. When one attempts to activate the windshield wipers, the torque of the motor applied through a driving linkage for oscillating the wipers may be insufficient to overcome the force with which the wipers are adhered to the windshield. The wiper blades may simply not move as the torque is applied which requires that the driver leave the car and manually break the adhesion between the windshield wiper blades and windshield. This is, of course, an undesirable aggravation. Further still, the linkage which connects the windshield wipers to the motor may fail if the torque of the motor is too high or a fuse may blow, resulting in wipers which are inoperable. Drivers who must use their vehicles immediately or who are impatient may then be tempted to drive without operating windshield wipers which is, of course, especially hazardous in winter when windshields can become covered with salt and sand, obscuring the driver's vision. Even if the blades of the windshield wiper are not adhered, there is the difficulty of wiper blades having deposits of ice thereon which at least initially compromises their effectiveness. Accordingly, there is a need for an arrangement which prevents adhesion of windshield wiper blades to windshields and which prevents the accumulation of ice, frozen snow and frost on wiper blades. The problem is recognized in the prior art in patents such as U.S. Patent 4,549,471 to Kochy et al. in which heated air from a defroster system is directed by secondary air ducts to an area of the windshield where windshield wiper blades rest when the wipers are parked. A difficulty with this approach is that it is necessary to warm up the engine and heat the cooling fluid of the engine to a relatively high level before heated air is available for application to the windshield. This may take a considerable amount of time, especially on very cold days and tempt the driver to activate the windshield wipers before the ice or snow adhering the wipers the windshield has melted which can result in damage to the wipers or perhaps a blown fuse as described above. Another approach is set forth in U.S. Patent 3,738,252 to Cardinale wherein a hot water radiator is disposed proximate the windshield wiper blade when the windshield wiper is in its parked position. Again, it takes time to heat the coolant to a level sufficient to begin melting ice during which time the driver may attempt to activate the windshield wipers before the ice is melted. Perhaps in recognition of the deficiencies of arrangements such as those of Kochy et al. and Cardinale, U.S. Patent 5,173,586 to Gold discloses positioning an electric heater on the outside of the windshield just below the wiper blade. This is, however, a complex relatively expensive arrangement wherein the heater for the wiper blade must be protected against moisture, wind and general environmental degradation due to exposure on the outside of the windshield. The heater is subjected to engine heat as well as moisture, low temperatures and wind-induced pressure differentials, all of which combine to comprise its reliability. The heater is subjected to the greatest environmental stress at a time when it is needed most and is thus more likely to fail at a time it is needed most. In view of the aforementioned considerations, there is a need for an arrangement to heat windshield wiper blades when in their parked mode, wherein the arrangement is relatively inexpensive, reliable and has a relatively rapid response time. Other windshield heating arrangements are disclosed in EP-A-0013970, and EP-A-0524537, JP-A-2144427, GB-A-506700, DE-B-2507037, and AT-A-375605. Reference EP-A-0013970 discloses, in one embodiment, heating wires arranged along a full width of the lower end area of the windshield. In another embodiment, EP-A-0013970 discloses heating wires arranged at less than the full width of the windshield and sandwiched between the windshield layers. Reference EP-A-0 052437 discloses use of an electro-conductive coating (18) to heat the upper part of the windshield and an additional heating grid over substantially an entire lower area of the coated windshield. Reference JP-A-2144247 discloses distinct heating wires for each of the wiper blades. Reference GB-A-506700 is directed to window panes in general and discloses wire patterns covering the entire area of the window pane. DE-B-2507037 discloses a heating arrangement for a rear windshield and single wiper blade combination where a heating grid includes a first section to heat the upper part of the windshield and a second section to heat where the wiper blade rests when it is not oscillating. Lastly, reference AT-A-375605 shows heating elements in contact with an inside surface of an automobile windshield so as to heat an entire lower portion of the windshield, including where side by side wiper blades rest when parked, and a power circuit for supplying current to the heating elements. It is an object of the present invention to provide a new and improved arrangement for heating windshield wiper blades when windshield wipers are in a parked mode. According to the present invention, there is provided a windshield heating assembly including an automobile windshield having an inside surface and an outside surface including a parking area where a pair of windshield wiper blades rest when in a parked mode, a windshield wiper heater including an electric resistance heating element disposed in contact with said inside surface at an area aligned with said parking area of said outside surface, and a power circuit for supplying electric current connected to said heating element to melt ice or snow accumulated on said parking area around the windshield wiper blades, characterized in that the first of said wiper blades is disposed below the second of said wiper blades when in parked mode, and in that said heating element includes a grid local localized at the center of the windshield, said grid including three electric wires disposed in alignment with said parking area on said outer surface of said windshield so as to locally heat said parking area, the first of said wires being aligned with the lower windshield wiper blade (30), the second of said wires (44) being disposed between the lower and upper windshield wiper blades (30, 32), and the third of said wires (46) being aligned with the upper windshield wiper blade (32), said grid (40) including first and second ends (52, 54) joined to first and second busses (56, 58) which extend from said grid (40) to locations proximate to side edges of said windshield (12), said busses (56, 58) having leads (60,62) thereon for connection to the power circuit. Advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: Figure 1 is a side elevational view showing a windshield with a windshield wiper blade in its parked mode on the outside of the windshield and a windshield wiper heater, configured in accordance with the principles of the instant invention positioned on the inside of the windshield in alignment with the wiper blade; Figure 2 is a back view of the arrangement of Figure 1 showing the configuration of the heating elements comprising the electric heater; and Figure 3 is a circuit diagram showing an arrangement for integrating the electric heater for windshield wipers with a defrost system of the automotive vehicle. Referring now to Figures 1 and 2, there is shown an automotive vehicle 10 which has a windshield 12 which isolates the interior environment 14 of the vehicle from the external environment 16. Typically, the windshield 12 is fabricated of safety glass having an exterior panel 18 bonded to an interior panel 20 by a layer of adhesive 22. The windshield 12 has an exterior surface 24 which is exposed to the rigors of the external environment 16 and an interior surface 26 which is generally protected from the external environment since it is exposed primarily to the interior environment 14. As is seen in Figure 1, a pair of conventional windshield wipers 30 and 32 have rubber or synthetic rubber blades 34 and 36, respectively, which wipe the outer surface 24 of the windshield 10. In Figure 1, the windshield wipers 30 and 32 are shown in their parked mode at the bottom of the windshield. Upon activation of a conventional windshield wiper motor (not shown), the wipers 30 and 32 oscillate to clean the outer surface of the window 24 but when the automotive vehicle is not being used, the windshield wipers 30 and 32 are in the position of Figure 1. In cold, wet climates, snow and ice tend to accumulate around the windshield wipers and can adhere the windshield wiper blades 34 and 36 to the outer surface 24 of the windshield. This may occur due to a snow and ice storm or perhaps may occur when water kept liquid by the operation of a defrosting system or the vehicles engine freezes when the vehicle is not being used. In accordance with the features of the present invention, an electric grid 40 is disposed in alignment with the parking area 38 on the outer surface 24 of the windshield 10 so as to locally heat the parking area. In the preferred embodiment, the electric heating grid 40 is comprised of three wires 42, 44 and 46, each of which is in abutment with the back surface 26 of the windshield 10. The wire 42 is aligned with the wiper blade 34 of the lower windshield wiper 30 while the wire 46 is aligned with the wiper blade 36 of the upper windshield wiper 32. The wire 44 is disposed midway between the wires 42 and 46 so that the entire heating area 48 on the inside surface 26 of the windshield 10, disposed proximate the parking area 38 on the outside surface 24 of the windshield, is heated when the grid 40 is energized. As is seen in Figure 2, the grid 40 is localized at the center of the windshield 12 with the heating wires 42, 44 and 46 converging at ends 52 and 54 to busses 56 and 58, respectively. The busses 56 and 58 have leads 60 and 62, respectively, which are connected to electrical power sources, as seen in Figure 3. The busses 56 and 58 each extend proximate the lower edge 64 well out of the view of the driver and allow heat to be concentrated where it is most needed, generally in the area 48 where the windshield wipers 30 and 32 are parked. Referring now to Figure 3 where a circuit diagram for a control circuit 70 is shown, it is seen that the lead 60 connects the grid 40 to climate control circuitry 40 and line 76 connects the lead 62 to a fuse. The climate control circuit includes a rotary switch 80 which rotates between a number of positions including an off position 82 and a defrost position 84. When the rotary switch 80 is in the defrost position, operating the defrost system of the automobile, the heating grid 40 is energized and current flows through the lines 42, 44 and 46, heating the area 48 in the windshield. As long as the climate control system 74 is in the defrost mode, the grid will remain energized to deice wiper blades 34 and 36 (see Figure 1). When the switch 80 is not rotated from the off to the defrost position, the grid 40 comprising the electric wiper deicer may still be operated by switch 86. The switch 86 includes a conventional timer 88 connected thereto which times out after 10 minutes, opening the switch 86 and interrupting current to the heating grid 40. Thus, the heating grid 40 may be activated by either the climate control system 74 of the automotive vehicle or by a separate isolated switch 86. Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever. In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius and unless otherwise indicated, all parts and percentages are by weight. EXAMPLE The following table is an example of a preferred grid system for a vehicular windshield which has worked effectively with the thickness of the wires being approximately 0.0005 inches (12.7 micrometers). STUDY OF EWD (VERSION 3c) THREE PARALLEL GRID LINES BUSS LEFT TOP MIDDLE BOTTOM BUSS RIGHT LENGTH mm 394 1029.7 954.7 888 394 WIDTH mm 7 0.8 0.6 0.6 7 Reach ohm 0.263844 6.033527 7.458752 6.906397 0.263844 Rsegment ohm 0.263844 2.249190 0.263844 Rewd ohm 2.776879 Vewd volts 13 lewd amp 4.681513 leach amp 4.681513 1.745183 1.411712 1.524617 4.681513 Peach watt 5.782574 18.37610 14.86478 16.05363 5.782574 Pneeded (P/A = 0.5 watt/in) 73% -10% -26% -8% 73% P/A 0.73 0.45 0.40 0.46 0.37 In the above table, denotion "ewd" means "electric window defrost" and the other denotions being self-explanatory. The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

Claims: A windshield heating assembly including an automobile windshield (12) having an inside surface (26) and an outside surface (24) including a parking area where a pair of windshield wiper blades (30,32) rest when in a parked mode, a windshield wiper heater including an electric resistance heating element disposed in contact with said inside surface (26) at an area aligned with said parking area of said outside surface (24), and a power circuit for supplying electric current connected to said heating element to melt ice or snow accumulated on said parking area around the windshield wiper blades, characterized in that the first of said wiper blades (30) is disposed below the second of said wiper blades (32) when in parked mode, and in that said heating element includes a grid localized at the center of the windshield (12), said grid (40) including three electric wires (42, 44, 46) disposed in alignment with said parking area on said outer surface (24) of said windshield (12) so as to locally heat said parking area, the first of said wires (42) being aligned with the lower windshield wiper blade (30), the second of said wires (44) being disposed between the lower and upper windshield wiper blades (30, 32), and the third of said wires (46) being aligned with the upper windshield wiper blade (32), said grid (40) including first and second ends (52, 54) joined to first and second busses (56, 58) which extend from said grid (40) to locations proximate to side edges of said windshield (12), said busses (56, 58) having leads (60, 62) thereon for connection to the power circuit. A windshield heating assembly according to claim 1 characterized in that the parking area on the outside surface (24) of the windshield (12) is spaced by selected distances from side edges of the windshield (12), and in that the grid (40) is disposed only in an area aligned with the parking area. A windshield heating assembly according to claim 1 or 2, characterized in that the power circuit further includes a climate control system for an automobile interior, said climate control system having a defrost setting (84) that causes air to heat the inside surface (26) of the windshield (12), said climate control system having a mode control switch (84) connected to the grid (40) such that when said switch (84) is in a defrost setting said grid (40) is energized. A windshield heating assembly according to any of claims 1 to 3, characterized further by a deicing switch (86) coupled to the power circuit in parallel with the mode control switch (84) to connect the grid (40) to the power source independently of the mode control switch's (84) defrost setting, said deicing switch (86) having a timer (88) to open said switch (86) after a selected period of time so as to interrupt power to said grid (40). A windshield heating assembly according to any of claims 1 to 4, characterized in that the electric wires (42, 44, 46) of the grid (40) each have a diameter of substantially 12.7 micrometers (0.0005 inches). A windshield heating assembly according to any of claims 1 to 5, characterized in that the wires (42, 44, 46) of the grid (40) have a resistance in the range of substantially 6.0 to substantially 7.5 ohms.

Inventors: KNUDSEN WILLIAM, KNUDSEN, WILLIAM
Applicants: CHRYSLER CORP, CHRYSLER CORPORATION
Application year: 1994
Main classification: B60S1
IPC codes: H05B3, B60S1